To examine the influence of time of day on the GH and cortisol response to exercise, 10 healthy young men will exercise (lactate threshold) for 30 min. at 3 different times of day (0000, 0700, 1900 h). Subjects will receive a standard meal and then be fasted for 12 h prior to the 6 h sampling period. There will be a control day (no exercise) and an exercise day at all 3 times of day. CORE LAB ONLY